Cafelat Robot Piston Seal Life

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#1: Post by mborkow »

Branching off the main Cafelat Robot thread as that one has become so long...

I last replaced my Cafelat Robot piston seal on March 7th (documented in this post). Since that time (131 days), I've pulled around 400 shots (~3 shots per day with an occasional extra shot here and there). This AM, my first two attempts to pull a shot were...failures. I had trouble locking in the portafilter and when I could get it locked in I had water dribbling out of the sides. First I took off the existing seal and tried reseating and re-lubing it...but the PF action still felt really clunky and I couldn't get it locked in smoothly. Since I had an extra seal on hand, I installed it, applied a little molykote, and have pulled two nice shots since (no water dribbling out the side and no problem locking in the PF).

400 shots on a $5 seal seems pretty good to me, but I am wondering: how many shots are others getting out of their seal?


#2: Post by jpender »

For me it's been close to double the shots you got. Some people get years out of a seal. Thousands of shots.

Cafelat Robot piston seal life

Cafelat Robot Gaskets Failing Quickly

mborkow (original poster)
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#3: Post by mborkow (original poster) »

Oh dear...I seem to have made the rookie mistake of starting the same thread for a third time :oops:


#4: Post by jpender »

Oh it's okay. I just thought you might like to see what others have said already.

AFAIK nobody has figured out why some seals die early and others are practically immortal. That would be interesting to learn.

mborkow (original poster)
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#5: Post by mborkow (original poster) »

I just quickly perused those other threads. Although others do seem to have forever-seals, 400 doesn't seem short to me...though I wouldn't mind extending that lifetime (that's just my natural frugality). I wonder if we could develop/determine a set of best practices for extending seal life. Based off only my own usage, I wonder if I should lube it more often...I have a full tube of Molykote (so more than a lifetime's supply for my usage) so I could lube it monthly or weekly if that would help. I see some have speculated that storing the PF off the Robot would extend life but I am already doing that (and the anecdotal evidence at my disposal seems not to support that theory anyway).


#6: Post by jpender »

I don't know. I recall others, including Paul, saying that they rarely if ever lube the seal and still get long life.

It's not a big deal since the seals are inexpensive, available, and also have a long shelf life. But it's curious. A mystery.

mborkow (original poster)
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#7: Post by mborkow (original poster) replying to jpender »

I didn't mean for anyone to infer I thought this was a problem. It isn't; everything mechanical has a maintenance interval and seals are wear items.

I have just placed an order for 4 more seals (for the grand total of $20) and that will see me through at least the next 20 months. I don't want to mess with the good seal I have in place now while I don't have a back up, but once I do get this order in I will try again to reseat the seal I just took off. It could be in my pre-coffee state I didn't do a great job of reseating it (which Paul, based on other threads, indicates is the likely culprit).


#8: Post by jpender »

If I recall correctly, Paul said that was the most likely cause for a newer seal "failure". Maybe that's the case with yours?

It's not that difficult or risky to remove and install a seal. They are very stretchy and resilient. Just don't use anything sharp as you could tear it that way. I can usually pull one off with just my fingers but on occasion have used a blunt tool to get it started. Once lubed I find they pop into place quite easily. You can see if it's in there correctly.

At some point they do change. It's visually apparent that they enlarge with use but it's not at all clear if that's a problem or not.

mborkow (original poster)
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#9: Post by mborkow (original poster) »

jpender wrote:It's not that difficult or risky to remove and install a seal
True...but everything's exactly as I want it to be now...and I don't want to let my curiosity mess it up (and if I can't make my wife her morning shot tomorrow, I'm in big trouble!)


#10: Post by Nate42 »

There is probably some minor variation from seal to seal, or some luck factor. My first seal lasted for years. My second seal is 1 year old now and while it still works it's regularly coming out of the groove. I won't be surprised to see it fails much earlier than previous.